Electrically motorized wheel assembly provided with a peripheral filler

ABSTRACT

An electrically motorized wheel assembly comprising a hollow shaft having a first opening at one end thereof and a second opening, the first opening receiving conductors from outside of assembly; a stator coaxial with and fixedly attached to the shaft; and a rotor coaxial with the stator and mounted for rotation about the stator, the rotor comprising a housing having a cylindrical wall having an inner surface provided with a magnetic means surrounding the stator and separated therefrom by an air-gap. The motorized wheel assembly also comprises a cylindrical filler made of a resilient material, the filler having a smooth outer surface and being waterproof, the filler being mounted around the housing, whereby the filler prevents presence of dirt and unwanted impurities between the housing and a rim fixed around an outer surface of the housing.

FIELD OF THE INVENTION

The present invention is concerned with an electrically motorized wheelassembly.

BACKGROUND OF THE INVENTION

Known in the art, there is the U.S. Pat. No. 4,913,258 of HiroshiSAKURAI et al, granted on Apr. 3, 1990, in which there is described anouter-rotor type motor wheel, comprising a knuckle, a hub coaxiallyinterlocked with the knuckle, a wheel disc rotatably attached to theperiphery of the hub, a wheel secured to the periphery of the wheeldisc, a rotor fastened to an outer side of the wheel disc from thedirection of the outer side, and a stator coaxial to and spaced from therotor by a small gap and fastened to the hub from the direction of theouter side. One drawback with this outer-rotor type motor wheel, is thatin order to provide a powerful motor wheel having a high torque, highcurrent has to be injected to the power line to energize the coil of thearmature core even at zero speed. With this outer-rotor type motorwheel, a converter has to be provided. This converter is mounted insidethe vehicle and can be very cumbersome. Such high current circulatingthrough the power line produces heat which is energy loss and alsorequires a power line which can be quite heavy.

Also known in the art, there is the U.S. Pat. No. 754,802 of FerdinandPORSCHE et al, granted on Mar. 15, 1904, in which there is described thecombination of the axle, the wheel, the hollow journal for the wheel,the end of the axle projecting to the journal, and a pivotal connectionbetween the axle and journal having its axial line disposed acutely tothe plane of the wheel. Again, to produce a powerful motor-wheel, thecurrent supplied to the sliding brushes, brought from outside of themotor-wheel has to be a high current. This high current will have to bebrought through large diameter cables or wires to reduce energy loss.

Also known in the art, there is the U.S. Pat. No. 2,348,053 of J. E.BOWKER, granted on May 2, 1944, in which there is described anelectrically-operated motor vehicle improvements comprising a pluralityof wheels arranged to be driven, a dynamotor forming an integral part ofeach such wheel, and electrical circuit connections between switch banksand dynamotors and batteries to control the operation of the dynamotorsas motors according to the position of a selector switch. Again, thearmature windings will have to be energized with a high current in orderto produce a powerful motor, such high current will require largediameter cables to bring the energy from the batteries of the vehicle tothe windings of the armature. As well known, such large diameter cablesor wires are rigid, cumbersome and inconvenient.

Also known in the art, there are the following U.S. Pat. Nos. thatdescribe different kinds of motor-wheels 638,643; 643,854; 2,348,053;2,506,146; 2,514,460; 2,581,551; 2,608,598; 3,566,165; 3,704,759;3,792,742; 3,812,928; 3,892,300; 3,897,843; 4,021,690; 4,346,777;4,389,586; 1,709,255; 2,335,398; 3,548,965; 4,913,258.

None of the above-mentioned patents shows the necessary means forpreventing presence of dirt and unwanted impurities between the housingof the rotor and a rim fixed around an outer surface of the housing.

It is an object of the present invention to provide an electricallymotorized wheel assembly comprising a means for preventing presence ofdirt and unwanted impurities between the housing of the rotor and a rimfixed around the outer surface of the housing.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an electricallymotorized wheel assembly comprising:

a hollow shaft having a first opening at one end thereof and a secondopening, said first opening receiving conductors from outside of saidassembly;

a stator coaxial with and fixedly attached to said shaft, said statorcomprises a central portion attached to said shaft, a support extendingradially from said central portion, and a peripheral circular polepiece, said pole piece being fixed onto peripheral ends of said support;

a rotor coaxial with said stator and mounted for rotation about saidstator, said rotor comprising a housing having a cylindrical wall havingan inner surface provided with a magnetic means surrounding said statorand separated therefrom by an air-gap, said housing comprising an innerwall, on a side of said cylindrical wall, and an outer wall, on theother side of said cylindrical wall, said shaft extending through saidinner wall and centrally thereof;

a cylindrical filler made of a resilient material, said filler beingwaterproof, said filler being mounted around said housing, whereby saidfiller prevents presence of dirt and unwanted impurities between saidhousing and a rim fixed around an outer surface of said housing.

Further objects, advantages and other features of the present inventionwill become more apparent upon reading of the following non-restrictivedescription of preferred embodiments thereof given for the purpose ofexemplification only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view partially in cross-section of anembodiment of the present motorized wheel assembly, in combination witha rim, a tire and a knuckle-jointed connecting rod;

FIG. 2 is a front view partially in cross-section of the rotor andstator of the motorized wheel assembly shown in FIG. 1, details ofcentral core note included;

FIG. 3 is an enlarged detail of FIG. 1;

FIG. 4 is a view along line 4--4 of FIG. 3;

FIG. 5 is a front view of a portion of the motorized wheel assemblyshown in FIG. 1;

FIG. 6 is an enlarged detail of FIG. 1;

FIG. 7 is a cross-section view along line 7--7 of FIG. 5;

FIG. 8 is a front view of the rim with the tire shown in FIG. 1;

FIG. 9 is a cross-section view along line 9--9 of FIG. 8;

FIG. 10 is an enlarged detail of FIG. 9;

FIG. 11 is an enlarged detail of FIG. 9;

FIG. 12 is an enlarged detail of FIG. 1;

FIG. 13 is a rear view of the elements shown on FIG. 12;

FIG. 14 is a rear view of the knuckle-jointed connecting rod shown onFIG. 1, partially in cross-section;

FIG. 15 is a rear view of an element of FIG. 1 onto which theknuckle-jointed connecting rod is connected;

FIG. 16, is a view from above partially in cross-section of the rearpart of the motorized wheel assembly shown in FIG. 1;

FIG. 17 is a rear view of the knuckle-jointed connecting rod incombination with a disk-brake;

FIG. 18 is a schematic block diagram of an electrical converting systemin accordance with the present invention.

FIG. 19 is a side elevational view partially in cross-section of anotherembodiment of the motorized wheel assembly in accordance with thepresent invention;

FIG. 20 is a side elevational view partially in cross-section of anotherembodiment of the motorized wheel assembly in accordance with thepresent invention.

FIG. 21 is a schematic block diagram of another embodiment of theelectrical converting means in accordance with the present invention.

FIG. 22 is a side elevational view partially in cross-section of anotherembodiment of the motorized wheel assembly in accordance with thepresent invention.

FIG. 23 is a front view partially in cross-section of the stator androtor the motorized wheel assembly shown in FIG. 22;

FIG. 24 is another side elevational view, partially in cross-section ofthe embodiment of the motorized wheel assembly shown in FIG. 1; and

FIG. 25 is an enlarged detail of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to FIGS. 1 and 2, there is shown respectively a sideelevational view partially in cross-section of an embodiment of themotorized wheel assembly, in combination with a rim 28, a tire 32 and aknuckle-jointed connecting rod 50; and a front view partially incross-section of the rotor 10 and stator 6 of the motorized wheelassembly shown in FIG. 1. The electrically motorized wheel assemblycomprises a hollow shaft 2 having a first opening at one end thereof andsecond openings. The first opening receives conductors 4 from outside ofthe assembly. The stator 6 is coaxial with and fixedly attached to theshaft 2, the stator 6 being provided with hollow portions 11 and coils8. In FIG. 2, only a few coil sections are indicated by number 8 but itis meant to indicate the coils all around the stator 6. The stator 6 isfixedly attached to the shaft 2 but it can be removed therefrom when theassembly is not operating. The rotor 10 is coaxial with the stator 6 andmounted for rotation about the stator 6. The stator 6 includes openingsforming the hollow portions 11 between radiating arms 13 to reduce itsweight. The assembly is also provided with a converting system 12 forconverting an input electrical current to a variable AC electricalcurrent. The converting system 12 includes a microprocessor unit 44, aDC/AC converter having power electronics 14 fixedly mounted within thehollow portions 11, input terminals 15 for receiving the inputelectrical current brought by means of the conductors 4 and outputterminals 16 for delivering the variable AC electrical current. It hasto be understood that the converting system can be reversible, in such away that the assembly can be used as a generator. The frequency of thevariable AC current relates to the desired rotation speed of the rotor10, the phase angle of the variable AC current determines whether theassembly will operate as a motor or as a generator, and the amplitude ofthe variable AC current relates to the desired torgue.

The user of the present assembly can use relatively low diameterconductors to bring electrical power inside the assembly if such poweris produced by a high voltage because the power electronics 14 areinside the assembly. Such power electronics 14 will convert the highvoltage low current input signals into a high current signal to supplythe variable AC current to the coils 8 of the stator. Because the powerelectronics 14 are already inside the assembly, the large diameter wiresneeded to bring the electrical current from the converting system 12 tothe coils 8 of the stator will be relatively short. It is understoodthat the power electronics 14 comprise capacitors, transistors, diodesand other components as is well known in the art.

To reduce the weight or the diameter of the electrical conductors, ahigh voltage supply can be used in accordance with the relation P=IV,where P is power, I is current and V is voltage. If V is increased, thenI is reduced. At low speed, power is low. This implies that the currentwhich supplies the converter is low because the voltage is constant.But, if a high torque is needed, the current that supplies the coils ofthe stator has to be high. The mounting of the power electronics of theconverter inside the housing allows for a selection of the electricalsupply conductors with respect to a desired motor power while allowinghigh torque at low speed. Furthermore, the converter allows a matchingof the motor impedance with respect to the one of the high voltagesupply source.

The stator 6 comprises a central portion attached to the shaft 2, arms13 extending radially from the central portion, and a peripheralcircular pole piece including metallic strips 27 wound with the coils 8.The pole piece is fixed onto peripheral ends of the arms 13.

The rotor 10 comprises a housing having a cylindrical wall 17 havinginner surface provided with magnetic means 26 surrounding the stator 6and separate therefrom by an air gap. As the air gap is relativelysmall, it cannot be seen in these FIGS. 1 and 2 but its location isindicated in FIG. 25 by means of R₁. The housing comprises an inner wall18 on one side of the cylindrical wall 17, and another wall 20 on theother side of the cylindrical wall 17. The shaft 2 extends through theinner wall 18 and centrally thereof.

The housing integral with the rotor 10 sealingly encloses the shaft 2,the stator 6 and the converting system 12. An airtight joint 123 isprovided. The assembly comprises a first bearing 22 associated with theinner wall 18, and a second bearing 24 associated with the outer wall20. The bearings 22 and 24 are respectively mounted on both sides of theshaft 2 so that the rotor 10 can be rotated with respect to the stator 6by means of the bearings 22 and 24. A threaded bolt 23 is provided forfixing the stator 6 with respect to the shaft 2. A stop ring 21 is alsoprovided. A compressed ring 127 is provided for fixing the bearing 22.

The stator 6 requires at least two arms between the openings to supportthe pole piece of the stator 6. Also, the support can comprise threeequally spaced arms extending radially to the peripheral ends of thestator 6. In FIG. 2, it can be seen that the stator 6 comprises fourequally spaced arms 13. In the embodiment shown in these FIGS. 1 and 2,the magnetic means of the rotor 10 includes a series of permanentmagnets 26. In FIG. 2, only some magnets are identified by the number 26but it has to be understood these magnets 26 are provided all around thestator 6. The stator 6 is partially made of a light weight heatconductive material. Preferably, this material is an aluminum alloy. Theassembly further comprises a rim 28 fixed around an outer surface of thehousing, and a cylindrical filler 30 made of a resilient material. Thefiller 30 has a smooth outer surface and is waterproof. The filler 30 isa layer made of elastomer. The rim 28 is adapted to receive the tire 32.The rim 28 is flat. The magnets 26 are made preferably of neodymium,iron and boron. The filler 30 prevents penetration of water or dustbetween the housing and the rim 28 and consequently reduces corrosionthereof.

The filler 30 has to be resilient at temperatures of the order of -55°C. to 100° C. The filler 30 has a smooth outer surface so that it allowsan easy mounting of the rim 28 around the housing of the rotor 10. Thefiller 30 is waterproof and has to withstand corrosion produced bycorrosive elements of the road. Also, it has to withstand ultravioletrays.

The peripheral ends of the arms 13 are fixed onto the pole piece of thestator 6 by means of a circular member 34 which is integral with theperipheral ends of the arms 13. The circular member 34 has its outersurface provided with recesses 36. The circular pole piece of the stator6 has an inner surface provided with projecting tongues 37 ofcomplementary shape that can be fitted into the recesses 36 for fixingthe pole piece of the stator 6 onto the circular member 34. The circularmember 34 has an inner surface provided with projections 38, whereby anefficient heat exchange can be obtained by means of the projections 38when an air circulation is produced inside the housing. Only a fewprojections are indicated by the number 38 to not overload FIG. 2. Thesupport of the stator 6 and the circular member 34 are made of analuminium alloy whereas the pole piece of the stator 6 is made of steel.

It has to be noted that the ends of the cross formed by the arms 13 ofthe stator 6 are aligned with the recesses 36 for mechanical reasons.Also, the projections 38 that are disposed along said circular member 34are in respect of their longitudinal dimension preferably offset withrespect to the axis of the shaft of the motorized wheel assembly, alongthe circumferential direction of the member 34 to mechanicallystrengthen it.

Referring now to FIGS. 1, 2 and 25, the air gap is positioned at apredetermined distance R₁ from the central axis 3 of the shaft 2. Therim 28 has a surface 29 for receiving the tire 32 that is positioned ata predetermined distance R₂ from the central axis 3 of the shaft 2. R₁/R₂ should be substantially between 0.65 and 0.91 to have an efficientassembly. The higher the ratio R₁ /R₂ is, the better the efficiency ofthe assembly is. But, as there is physical limitation, the assemblyshown in FIGS. 1, 2 and 25 has substantially a ratio R₁ /R₂ of 0.91.

For a motor with a radial air-gap, torque T is proportional to L.R₁².I_(B), where L is pole width, R₁ is radius of air gap and I_(B) iscoil current. In designing the present assembly, the width L of the polepiece has been maximized. By having many poles, the weight of the polarpiece of the magnetic circuit can be reduced to consequently reduce theweight of the rotor and the inertia moment of the rotor, and to allow acavity for mounting a brake means. The present assembly increases thetorque T by a wide polar piece and by a high ratio of R₁ /R₂ where thetheoretical limit that cannot be reached is 1. The present assembly alsoprovides a high power because P=T.ω which is proportional to L.R₁ ².I.ω,where ω is the angular frequency of the rotor. The present assemblycomprises a cross-shaped stator to reduce weight of the assembly, toallow cooling of the coils, and to allow space in hollow portions 11 formounting the converting system. The cross-shaped stator supports theconverting system and is used as a heat sink.

The assembly has preferably thirty two poles. This assembly can alsooperate with sixteen poles, but it is preferable to have as many polesas possible to reduce the weight of the assembly. The conductors 4 arepreferably made of a coaxial cable incorporating an optical fiber. Thecoaxial cable prevents emission of radiation.

Please note that in the following description, the same referencenumbers are referring to similar elements throughout the drawings.

Referring now to FIGS. 1, 2 and 18, the converting system comprises aDC/AC converter has an input 40 for receiving a direct current from theinput terminals, and three outputs 42 for generating three phase ACcurrents into the output terminals 16. The AC currents are notnecessarily three phase currents, different polyphase currents can beused. The converting system also comprises a microprocessor unit 44connected to the converter arms 41a, 41b and 41c for controllingoperation thereof, which microprocessor unit can be located outside ofthe motor wheel assembly. The converting system shown in FIG. 18 can beused when the rotor has not to be supplied with an electrical current.As it can be seen in FIG. 2, the stator 6 is cross-shaped and has fourarms 13. The converter includes three converter arms 41a, 41b and 41cthat generate respectively the three phase AC currents, the arms 41a,41b and 41c being fixed respectively to three of the four arms 13 of thestator 6. These three converter arms 41a, 41b and 41c are parts of thepower electronics 14 shown on FIG. 2. The power electronics 14 shown onFIG. 2 comprise the converter arms 41a, 41b and 41c shown on FIG. 18 butalso comprise the capacitor 43 shown on FIG. 18. In this FIG. 18, onlyone capacitor 43 is shown to simplify the FIG. 18 but in the embodimentshown in FIG. 2, the capacitor 43 is distributed in three capacitorsdisposed respectively on three of the four arms 13 shown in FIG. 2. Itis not essential that the command amplifiers 91 be inside the housing.Each of the converter arms 41a, 41b and 41c comprises a switchingsection and a command section which is the command amplifier 91. Themicroprocessor unit 44 is fixed onto the fourth arm. It should be notedthat the microprocessor unit 44 can be also mounted outside of theassembly because it does not generate a high current. The assemblyfurther comprises two circular supply distribution bus 48 connected tothe converter arms 41a, 41b and 41c, and the microprocessor unit 44,whereby the direct current brought by the conductors can be distributedto the converter arms 41a, 41b and 41c, and the microprocessor unit 44,by means of the bus 48. Please note that the converter can be an AC/ACconverter where a high voltage AC electrical current is brought by theconductors.

Referring now to FIGS. 1, 12, 13, 14 and 15, it can be seen that theshaft 2 is provided with a connecting means at its first end by whichthe assembly can be connected to a supporting member. This supportingmember is a knuckle-jointed connecting rod 50. This connecting means ismade of an annular member 52 having its outer edge regularly providedwith recesses 54 alternating with projections 56 so that the annularmembers 52 can be engaged and locked with a complementary part 53 of theknuckle-jointed connecting rod 50.

The projections 56 of the outer edge have width which varies in thecircumferential direction. The complementary part of the knuckle-jointedconnecting rod 50 has also an annular section 58 having a sufficientdiameter so that the annular section 58 can be slid over the outer edgeof the shaft 2. The annular section 58 has recesses 60 and projections62 of complementary shape adapted to cooperate with the correspondingprojections 56 and recesses 54 of the outer edge of annular member 52.The projections 62 of the annular section 58 has width which varies inthe circumferential direction so that the annular section 58 can be slidover the outer edge and rotated with respect with the outer edge to bewedged in an assembled position. Also, there is provided a key member 66having tongues 68 that can be inserted into cavities 55 that areproduced when the annular section 58 is rotated with respect to theouter edge of the shaft 2 to lock the shaft 2 with respect to theknuckled-jointed connecting rod 50. Holes 63 are provided for fixing adisk brake (shown in FIGS. 16 and 17).

The knuckled-jointed connecting rod 50 is provided with an innerelongated slot 70 having a first end adjacent to the annular sections58, and a second end adjacent to the other extremity of the rod 50whereby the conductors 4 can be brought to the shaft 2 along theelongated slot 70. The key member 66 has an elongated section 72provided with an inner elongated recess, the elongated section 72cooperating with the inner slot 70 of the rod 50 along a portion of itslength to protect the conductors 4. The portion of the slot 70 that isnot protected by the elongated section 72, is provided with a protectiveelement (not shown) to cover the conductor 4. It has to be noted thatthe inferior edge of the tongues 68 is slightly biased to allow easypenetration and locking of the tongues 68 in the cavities 55. Holes 65are provided for fixing the key member 66 onto the shaft 2. Threadedholes 67 are provided for making easy removing of the key member 66.

Referring now more specifically to FIG. 15, the first end of the shafthas an inner portion provided with a cavity 74 having sharp edges 76 inthe form of square corners so that it can receive a key (not shown inthe figures) for rotating the shaft 2.

Referring now more specifically to FIGS. 1, 18 and 25, a measuring meansfor measuring rotation speed and position of the rotor 10 with respectto the stator 6 comprises an optical fibre 80 having a first endconnected to the microprocessor unit 44, and a second end positioned tobe adjacent to the rotor 10. The measuring means also comprises acircular light reflector 82 mounted onto the rotor 10 in such a mannerthat when the rotor 10 is rotating, the reflector passes in front of thesecond end of the fibre 80, whereby the rotation speed and position ofthe rotor 10 with respect to the stator 6 can be calculated by means ofthe microprocessor unit 44. Please note that the circular reflector 82is made of a series of reflectors having different reflectingcharacteristics so that position of the rotor 10 with respect to thestator 6 can be determined at any time. The optical fiber 80 comprisesat least one fiber.

Referring now more specifically to FIG. 18, the optical fibre 80 and thereflector 82 form an encoder which is connected to a position decoder 83of the microprocessor unit 44. The position decoder 83 comprises anoptical coupler, a light source, a photodetector and other electroniccomponents. The microprocessor unit 44 also comprises a controller 85having an input 87 for detecting current in the coils 8 of the stator,and an output 89 for triggering said converter arms 41a, 41b and 41c bymeans of command amplifiers 91. The microprocessor unit 44 is alsoprovided with a communication interface 93 for linking it with anothercomputer device. It is not essential that the command amplifiers 91 beinside the housing.

Referring now to FIGS. 1, 16 and 17, it can be seen that the inner wall18 of the housing has a concave-shaped outer surface to produce, whenthe rotor 10 is rotating, an air circulation toward periphery of theinner wall 18. The outer surface being provided with a series ofparallel elongated strips 90 extending in the direction of the shaft 2.The strips have their free side defining the space 92 in which brakemeans 94 can be mounted, whereby an efficient heat exchange can beobtained through the inner wall 18 and the brake means 94 can be cooleddown by the air circulation produced along the inner wall 18.

Referring now more specifically to FIGS. 16 and 17, there is shown thatthe brake means 94 is a disk brake having its disk 96 bolted onto theinner wall 18. As it is known in the art, this disk brake comprises acalliper 98 adapted to cooperate with the disk 96. Shown in a schematicmanner, there is the ball joint 100 and the steering arm 102 of thesteering system. Each of the strips 90 is provided with a threadedcavity 104 for mounting a drum brake instead of the disk brake 94. Bolts95 are provided for fixing the disk 96 onto the inner wall 18.

There is shown the fasteners 106 for fixing the disk brake assembly 94onto the rod 50. There are also shown the bolts 108 to support thecalliper, and the pistons 110 for activating pads 99. From FIGS. 1, 16and 17 it can be seen that the ball joint of the steering system isquite close to the shaft 2 so that the angle α between the rotation axisof the motor-wheel and the axis determined by the rod 50 and theball-joint 100 is advantageous. It should be noted that the geometry ofthe inner wall 18 allows an advantageous position of the ball joint 100with respect to the motor-wheel assembly.

Referring now to FIGS. 1, 5, 6 and 7, the outer wall of the housingcomprises convex and concave sections 112 and 114 that alternate alongcircumference direction thereof, in such a manner that, when the rotor10 is rotating, an air circulation is produced inside the housing bymeans of the convex section 112 as indicated by the arrows 116, and anair circulation is produced along outside portions of the concavesection 114 as indicated by the arrows 118 whereby an efficient heatexchange can be obtained through the outer wall. It should be noted thatFIG. 6 is a side view partially in cross-section of FIG. 5. Apertureswith caps 113 are provided to have an access inside the housing. Bolts115 are provided for fixing the rim 28.

Referring now to FIGS. 1, 3 and 4, the assembly further comprises dryingmeans including an air pipe 120 having an end disposed inside thehousing, a chamber 122 disposed at the outer end of the pipe 120 and adesiccating material (not shown) disposed inside the chamber 122whereby, when the rotor 10 is rotating, air circulation is producedinside the pipe 120 and through the chamber 122 to dry air inside thehousing. The chamber 122 is annular, elongated and disposed inside thehollow shaft 2. The chamber 122 is opened at both of its ends. Theopening of the shaft that is adjacent to the knuckle-jointed connectingrod 50 is air tight. As it can be seen in FIG. 1, one end of the pipe120 is adjacent to the peripheral portion of the stator 6, the pipe 120is mounted between the outer wall 20 and the stator 6 till it reaches anopening in the shaft 2, then it is disposed along the chamber 122 withits other end 124 disposed at the end of the chamber as shown in FIGS. 3and 4. The end 124 of the pipe 120 is disposed between the air tightopening of the hollow shaft and the chamber 122 so that the aircirculating through the pipe 120 has to go through the chamber 122 whereit is dried.

The conductors 4 comprise at its centre, an optical fibre 126, a firstelectrical conductor 128 and a second electrical conductor 130 separatedfrom the first conductor by an isolating material 132. The conductors 4are protected by an outer sheath 134.

Referring now to FIGS. 8, 9, 10 and 11, there is shown a tire 32 that isfixed to the rim 28 in a permanent manner during the manufacturing ofthe assembly. The assembly is provided with a flat rim 28, a first sideflange 142 that is welded onto the rim 28, and a second side flange 144that is fixed onto the rim 28 by means of bolts 146 and L-shaped members148 welded onto the rim 28. The relation between the rim 28, the bolt146 and the L-shaped members 148 can be seen more easily on FIG. 10. Thetire 32 can be inflated by means of a valve 150 which provides an accessinside the tire 32. This valve 150 can be seen with more details in FIG.11.

As the rim 28 is flat, the tire 32 cannot be removed from the rim 28.With such motor-wheel assembly, when the tire is worn out, the rim 28with the tire 32 has to be replaced.

Referring now to FIG. 19, there is shown an assembly similar to the oneshown on FIG. 1, wherein the drying means is different. This dryingmeans include air pipe 120 having an end disposed inside the housing,and a chamber 121 with an inflatable balloon 123 mounted in a casing127, disposed at the other end 125 of the pipe 120. A desiccatingmaterial is disposed inside the chamber 121 whereby when temperature oratmospheric pressure changes, air circulation is produced inside thepipe 120 and through the chamber 121 to dry air inside the housing. Asit can be seen, the chamber 121 is disposed outside of the assembly. Theopening of the shaft 2 that is adjacent to the knuckle-jointedconnecting rod 50 is air-tight. The pipe 120 is used as an outlet fromand an inlet into the chamber 121.

Referring now to FIG. 20, there is shown an electrically motorized wheelassembly wherein the rotor comprises magnetic means including a polepiece made of metallic strips wound with a coil 9, the stator isprovided with brushes 111 that are connected to an output of theconverting system 12. The rotor is provided with conductive contactsurface disposed in a manner to cooperate with the brushes 111. Thecontact surface is connected to the coil 9 of the rotor 10.

Referring now more specifically to FIGS. 20 and 21, the convertingsystem 12 comprises a DC/AC converter having four converter arms 41a,41b, 41c and 41d, an input for receiving a direct current from inputterminals 40, and four outputs 45 and 43 for generating a DC current forcoil 9 of the rotor 10 and three phase AC currents for coils 8 of thestator 6. The converting system also comprises a microprocessor unit 44connected to the converter arms 41a, 41b, 41c and 41d for controllingoperation thereof. The coil 9 and the strips of the rotor 10 onto whichthe coil 9 is wound can be replaced by a conductive ring.

Referring now to FIGS. 22 and 23, there is shown a motorized wheelassembly incorporating an induction rotor. The rotor comprises amagnetic means including a pole piece made of metallic strips wound witha coil 9, whereby electrical current can be induced in the coil 9 of therotor by means of an electromagnetic field produced by electricalcurrent injected to the coils 8 of the stator 6. The reference number 8,in FIG. 23, is meant to represent all the coils disposed around thestator even if only one portion of the coils is indicated. Also,reference number 9, in FIG. 23 is meant to represent the coil that isdisposed all around the rotor. The converting system 12 comprises aDC/AC converter having three converter arms 41a, 41b and 41c, an inputfor receiving a direct current from the input terminals 15 that areconnected to the bus 48 and three outputs generating three phase ACcurrents into the output terminals 16. Also, the converting system 12comprises a microprocessor unit 44 connected to the converter forcontrolling its operation.

As it can be seen in FIG. 23, the stator 6 is cross-shaped and has fourarms 13. The converter comprises power electronics 14 which are made inparts of three converter arms that generate respectively the three phaseAC currents. The converter arms are fixed respectively onto three of thefour arms 13. The assembly further comprises two circular supplydistribution bus 48 connected to the power electronics 14 andmicroprocessor unit 44.

The air gap is positioned at a predetermined distance R₁ from thecentral axis 3 of the shaft 2. The rim 28 has a surface for receivingthe tire 32 that is positioned at a predetermined distance R₂ from thecentral axis 3 of the shaft 2. The ratio R₁ /R₂ is substantially between0.65 and 0.80 in the case where the rotor is provided with a coil. Thehigher the ratio is, the better the efficiency of the assembly is. Inthe case shown in FIGS. 22 and 23, the ratio is substantially 0.80.

Referring now to FIG. 24, there is shown that the stator 6 iscylindrical and provided with longitudinal and parallel slots 200 forreceiving the coils 8 of the stator 6. To not overload the FIG. 24, onlya few slots have been identified by number 200. The slots are bendedwith respect to the longitudinal axis 3 of the shaft 2 so that each ofthe slots 200 has its lower end that is substantially aligned with theupper end of the adjacent slot to provide a regular torque when theassembly is operating.

Although the present invention has been explained hereinabove by way ofpreferred embodiments thereof, it should be pointed out that anymodifications to these preferred embodiments within the scope of theappended claims is not deemed to alter or change the nature of the scopeof the present invention.

I claim:
 1. An electrically motorized wheel assembly comprising:a hollowshaft having a first opening at one end thereof and a second opening,said first opening receiving conductors from outside of said assembly; astator coaxial with and fixedly attached to said shaft, said statorcomprises a central portion attached to said shaft, a support extendingradially from said central portion, and a peripheral circular polepiece, said pole piece being fixed onto peripheral ends of said support;a rotor coaxial with said stator and mounted for rotation about saidstator, said rotor comprising a housing having a cylindrical wall havingan inner surface provided with a magnetic means surrounding said statorand separated therefrom by an air-gap, said housing comprising an innerwall, on a side of said cylindrical wall, and an outer wall, on theother side of said cylindrical wall, said shaft extending through saidinner wall and centrally thereof; a cylindrical filler made of aresilient material, said filler being waterproof, said filler beingmounted around said housing, whereby said filler prevents presence ofdirt and unwanted impurities between said housing and a rim fixed aroundan outer surface of said housing.
 2. An assembly according to claim 1,wherein said filler is a layer made of elastomer.
 3. An assemblyaccording to claim 2, wherein said filler withstands ultraviolet rays.4. An assembly according to claim 1, in combination with said rim fixedaround an outer surface of said housing.
 5. An assembly according toclaim 1, wherein said housing sealingly encloses said shaft and saidstator.
 6. An assembly according to claim 1, comprising a first bearingassociated with said inner wall, and a second bearing associated withsaid outer wall, said bearings being respectively mounted on both sidesof said shaft so that said rotor can be rotated with respect to saidstator by means of said bearings.
 7. An assembly according to claim 1,wherein said support comprises at least two arms between openingsprovided in said support to reduce its weight.
 8. An assembly accordingto claim 7, wherein said support comprises at least three equally spacedarms extending radially to said peripheral ends of said support.
 9. Anassembly according to claim 8, wherein said equally spaced arms comprisefour equally spaced arms.
 10. An assembly according to claim 1, whereinsaid stator comprises a lightweight heat conductive material.
 11. Anassembly according to claim 10, wherein said material is aluminiumalloy.
 12. An assembly according to claim 1, wherein said rim is flat.13. An assembly according to claim 1, wherein said outer wall of saidhousing comprises convex and concave sections that alternate alongcircumference direction thereof, in such a manner that, when said rotoris rotating, an air circulation is produced inside said housing by meansof said convex sections, and an air circulation is produced alongoutside portions of said concave sections, whereby an efficient heatexchange can be obtained through said outer wall.
 14. An assemblyaccording to claim 1, wherein said inner wall of said housing has aconcave-shaped outer surface to produce, when said rotor is rotating, anair circulation toward periphery of said inner wall, said outer surfacebeing provided with a series of parallel elongated strips extending inthe direction of said shaft, said strips having their free side defininga space in which brake means can be mounted, whereby an efficient heatexchange can be obtained through said inner wall, and said brake meanscan be cooled down by the air circulation produced along said innerwall.
 15. An assembly according to claim 1, wherein said shaft isprovided with a connecting means at its first end, by which saidassembly can be connected to a supporting member.
 16. An assemblyaccording to claim 1, wherein said air-gap is positioned at apredetermined distance R₁ from the central axis of said shaft, said rimhas a surface for receiving a tire that is positioned at a predetermineddistance R₂ from the central axis of said shaft, and R₁ /R₂ issubstantially between 0.65 and 0.91.
 17. An assembly according to claim16, wherein said rotor is provided with a coil, and wherein R₁ /R₂ issubstantially between 0.65 and 0.80.